1. Field of the Invention
The present invention relates to wireless communications, and more specifically, to a method and apparatus of transmitting data in a base station.
2. Related Art
The recent advent of the smartphone has sharply increased users' demand for support of good-quality data services. This led to the need of some technique that may support high data rate for terminals positioned at the edge of a cell, as well as terminals in the center of the cell. The center of each cell may enjoy increased data transmission speed simply by backing up the cell with additional antenna ports. However, in the edge of each cell, increasing data speed without cooperation between cells is limited by interference from the neighbor cells. Further, the frequency reuse technique through small cells such as pico cells or femto cells in a macrocell area is adopted in order to offer a high-speed data service even in a user-crowded region, and this results in the increased need for an efficient interference control method between transmission points.
The methods for controlling interference between transmission points are gaining attention. In particular, 3GPP (3rd Generation Partnership Project) denotes such interference control technique as CoMP (Coordinated Multi-Point transmission and reception) and is underway for standardization as an LTE-Advanced Release 11 work item.
The methods supported for CoMP in LTE-advanced release 11 may be divided into CS (Coordinated Scheduling), CB (Coordinated Beamforming), JP (Joint Processing), and DPS (Dynamic Point Selection). CS is a CoMP scheme that adjusts the time or frequency resources for transmission of signals to a terminal between transmission points in order to reduce interference on other transmission points. CB is a CoMP scheme that properly adjusts the direction of beams for transmission of signals between transmission points in order to reduce interference on other transmission points. JP is a CoMP scheme in which a plurality of transmission points perform simultaneous transmission to one terminal, and DPS is a CoMP scheme that dynamically varies transmission points considering the channel state of a terminal.